1. Field of the Invention
The present invention relates to an optical switching device, and more particularly to an optical switching device including a rib waveguide, a channel waveguide and a tapered waveguide.
2. Description of the Prior Art
In an optical communication technology and an optical device technology, a technology of manufacturing a thermo-optical digital optical switch and an arrayed waveguide grating multiplexing/demultiplexing router included in a planar waveguide-type optical device falls within a design/manufacture field of an optical device. The technology of manufacturing an optical switch may be classified as an optical switch technology of an optical device technology for an optical communication and falls within a waveguide-type digital optical switch design/manufacture technology using the thermo-optic effect of optical switch technologies.
Also, a technology of manufacturing a wavelength multiplexing device including an grating-arrayed optical waveguide may be classified as a wavelength multiplexing device technology using a wavelength division multiplex (WDM) method of an optical device technology for optical communication.
The waveguide-type optical switch includes a directional coupler, a X-switch, a two-mode interference switch, a switch using a Y-branch, etc.
The refractive indices of most of the conventional waveguide-type optical switches are periodically changed by the externally applied forces (voltage, pressure, heat, etc.) and switching is periodically changed accordingly. It is therefore impossible to use the conventional waveguide-type optical switches as a digital optical switch (DOS) that is switched as step-like.
In recent years, there has been an effort to develop a digital optical switch using a Y-branch. In order for this digital optical switch to be used in an actual optical communication switch, however, the performance of the crosstalk, the loss, etc. must be improved.
Recently, as the WDM method is used as a main method for increasing the capacity of the optical communication, an arrayed waveguide grating multiplexer/demultiplexer/router is used as a core element in the WDM optical communication system.
The arrayed waveguide grating multiplexer/demultiplexer/router multiplexes lights of various wavelengths into a single optical waveguide or demultiplexes lights of various wavelengths inputted from a single optical waveguide. Also, as the arrayed waveguide grating multiplexing/demultiplexing router allows the light of a specific wavelength to periodically reach a specific location, it has been widely used as a core element in an optical internet system, OXC and an optical exchange system. However, there is a problem that the performances of the crosstalk and the loss must be improved.
It is therefore an object of the present invention to provide an optical switching device capable of solving the above problems, wherein light input/output portions being a coupling portion with an optical fiber and a Y-branch portion are made of a rib waveguide, a bending (curving) portion is made of a channel waveguide, and the rib waveguide and the channel waveguide are connected by a tapered waveguide, in manufacturing a thermo-optic digital optical switch or an arrayed waveguide grating multiplexer/demultiplexer/router.
In order to accomplish the above object, an optical switching device according to the present invention comprises a plurality of light input portions connected to a plurality of optical fibers, respectively; a first Y branch portion for distributing lights outputted from each of the plurality of light input portions, the first Y branch portion have a plurality of Y branches; thermo-electrodes formed respectively at outsides of the Y branch to change refractive indices of the Y branch; a bending portion for controlling a path of the light selectively outputted from the first Y branch portion according to a variation of the refractive indices; a second Y branch portion for transmitting lights outputted from the bending portion; and a plurality of light output portions connected to the second Y branch portion, wherein the light input and the light output portions and the first and the second Y branches are composed of a rib waveguide, respectively; the bending portion is composed of a channel waveguide; and the first Y branch and the bending portion, and the bending portion and the second Y branch are connected by means of a tapered waveguide, respectively.
A planar waveguide-type Nxc3x97N digital optical switch having a plurality of Y branches comprises light input/output portions and Y-branches which are made of a rib waveguide, and a bending portion for connecting the Y-branches which is made of a channel waveguide, wherein the rib waveguide and the channel waveguide are connected by a tapered waveguide.
At this time, the difference in the effective indices between the rib waveguide and the channel waveguide is determined by the bending degree depending on the cross angle of the waveguide. Preferably, the difference in the effective indices of the rib waveguide is about 0.4% and the difference in the effective indices of the channel waveguide is about 0.6%.
Also, a wavelength multiplexing device including an arrayed waveguide grating according to the present Invention is characterized in that light input/output portions connected to a plurality of optical fibers, respectively, and an arrayed waveguide grating having a difference of refractive indices to make bending, the light input/output portions are fabricated by a rib waveguide, the arrayed waveguide grating is fabricated by a channel waveguide, and the rib waveguide and the channel waveguide are connected by a tapered waveguide.
At this time, the difference in the effective indices between the rib waveguide and the channel waveguide is determined by the bending degree of the waveguide. Preferably, the difference in the effective indices of the rib waveguide is about 0.6% and the difference in the effective indices of the channel waveguide is about 1.0%.